Abstract
Phyllosilicates, sulfates, and Fe oxides are the most prevalent secondary minerals detected on Mars from orbit and the surface, including in the Mars Science Laboratory Curiosity rover’s field site at Gale crater. These records of aqueous activity have been investigated in detail in Gale crater, where Curiosity’s X-ray diffractometer allows for direct observation and detailed characterization of mineral structure and abundance. This capability provides critical ground truthing to better understand how to interpret Martian mineralogy inferred from orbital datasets. Curiosity is about to leave behind phyllosilicate-rich strata for more sulfate-rich terrains, while the Mars 2020 Perseverance rover is in its early exploration of ancient sedimentary strata in Jezero crater. It is thus an appropriate time to review Gale crater’s mineral distribution from multiple perspectives, utilizing the range of chemical, mineralogical, and spectral measurements provided by orbital and in situ observations. This review compares orbital predictions of composition in Gale crater with higher fidelity (but more spatially restricted) in situ measurements by Curiosity, and we synthesize how this information contributes to our understanding of water-rock interaction in Gale crater. In the context of combining these disparate spatial scales, we also discuss implications for the larger understanding of martian surface evolution and the need for a wide range of data types and scales to properly reconstruct ancient geologic processes using remote methods.
Highlights
The past several decades of Mars exploration have demonstrated the breadth and variety of sedimentary processes on the surface of that planet (e.g., [1,2,3])
The purpose of this paper is to provide a synthesis of the current understanding of the geologic context of the most abundant secondary minerals explored far at Gale crater, how rover-based observations compare with orbiter-based interpretations, and to discuss the implications of these findings for future landed and orbital exploration, including deposits to be explored in Jezero crater by the NASA Perseverance rover
Though Curiosity is incapable of performing such techniques on the surface of Mars, CheMin is equipped with a novel sample holder that vibrates from a piezoelectric actuator drive
Summary
The past several decades of Mars exploration have demonstrated the breadth and variety of sedimentary processes on the surface of that planet (e.g., [1,2,3]). These three mineralogical periods correspond to terrains whose orbital-based visible-near infrared spectral reflectance signatures are indicative of the presence of clay minerals, sulfates, and anhydrous Fe oxides, respectively This framework provides a potentially powerful tool to link secondary mineralogy to changing climatic conditions, but the extent to which these mineral assemblages correlate with specific periods in geologic time and accurately record global (as opposed to local) atmospheric and near-surface conditions remains to be tested. This in situ exploration has led to a significant evolution in the understanding of the geologic history of this region as well as a clearer understanding of how secondary minerals in sedimentary strata observed from orbit translate to detailed depositional and post-depositional processes inferred from rover-scale observations.
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